Current Issue : October - December Volume : 2017 Issue Number : 4 Articles : 5 Articles
In high voltage input DC-DC converter, auxiliary winding of isolation transformer\nis usually used to supply power for control circuit. Due to the widerange\nof input voltage, the variable output voltage of auxiliary winding will\ncause a series of problems, such as variable drive pulse amplitude, increased\ndriver switching devices loss and drive transformer core saturation. This paper\nanalyzes the influence of variable output voltage of auxiliary winding in\ndetail. A novel method is proposed to solve the problem of large variation\nrange of auxiliary winding output voltage, which is adding a buck converter\nbetween the auxiliary winding and the control circuit. A dual switch forward\nconvert has been designed with 300 V - 800 V input and 24 V/5 A output. The\nresults show that this method is effective by comparing the different results of\nusing buck converter or not....
This paper investigates how to increase the efficiency of a photovoltaic/energy storage\ngeneration unit supplying dynamic loads by regulating and managing both the photovoltaic generator\nand the storage battery charge-discharge modes. The proposed photovoltaic/energy storage unit\nis proposed to supply an induction motor driven industrial pump with controlled speed and/or\na DC motor driven water pump. An optimal proportional-integral-derivative control based on an\nArtificial Bee Colony Optimization algorithm is used to regulate the photovoltaic generator in case of\nnormal operation or in case of maximum power point tracking (MPPT) and to also control the battery\nstorage charge discharge modes. A vector control based on the proposed optimal control is used to\nregulate the induction motor rotor speed at its low reference values needed by the industrial pump.\nFirst, a total model of the entire system is obtained. The controller performance with the proposed\nsystem is studied with both a DC motor and/or induction motor loads. Simulation results show that\nthe proposed photovoltaic/storage generator is able to supply the suggested dynamic loads under\ndifferent conditions and with good performance. Also, it is noticed that operating the photovoltaic\nbase on maximum power point tracking condition will give about 43% extra generation power than\nthe normal operation case....
Predictive control has attracted much attention and has been widely used in power\nelectronics and electric drives. However, further developments for applications in the field of\nrenewable energy systems are still under investigation. In this paper, the principles of predictive\ncontrol are studied with a focus on model predictive control (MPC) and vector-sequence-based\npredictive control (VPC). Based on these techniques, two control strategies for flexible power supply\nare developed. They are implemented in the most promising renewable energy systems, namely solar\nphotovoltaic (PV) systems and wind generators, respectively. The experimental results based on\na laboratory prototype show that the active and reactive powers supplied by the PV and wind\ngenerator can be controlled flexibly with excellent steady-state and transient performance. As the\npenetration level of the renewable energy sources in electricity network continues to rise, predictive\ncontrol tends to be an attractive and powerful technique for power electronics converters in renewable\nenergy systems....
In this paper, an efficient testing system for measuring a PV moduleââ?¬â?¢s I-V curve is proposed.\nThe proposed system is based on a controlled DC-DC boost converter. The advantage of using\na DC-DC converter is that this converter is typically used in PV systems to track the maximum power\npoint and to control the charging of the battery. Consequently, this device is utilized for I-V curve\nextraction without the need for further external devices. The I-V curve is extracted by modifying\nthe duty cycle of the triggering signal of the boost converterââ?¬â?¢s switch. The proposed system has\nbeen tested experimentally using a 120 Wp PV module. The results show that the proposed system\ncan successfully extract I-V curves of PV module. Notably, the performance of the tested module,\nas measured by this studyââ?¬â?¢s system as well as with a reference system, was found to be in the range\nof 61ââ?¬â??67% of the performance given in the datasheet. Hence, this result highlights the importance of\nconsidering a measurement of the actual performance of PV modules when designing any PV system\nso as to avoid an undersized system. The proposed I-V testing system can be used as a simple tool to\ndiagnose any shortages or low performance problems in PV system....
This paper dealt with the optimization of the performance of a photovoltaic\nmill system operating on the sun race. Depending on the characteristics of the\npowered load which is a DC motor driving a grain mill and on the weather\nconditions (temperature and illumination), we noted a very big difference\nbetween the potential maximum power and that actually transferred to the\nload. In order to improve the overall efficiency of the system, we use an adaptation\ncircuit consisting of a boost converter controlled by a numerical MPPT\n(Maximum Power Point Tracking) command. With the Perturb & Observe (P\n& O) algorithm, the MPPT control measure the photocurrent, the photo tension\nand the power released by the photovoltaic generator. From this result,\nthe MPPT control adjusts the duty cyclic of the converter to bring the system\nto the optimum operating point. Hence, using MATLAB/Simulink software,\nwe did the modeling and the simulation of the system which is composed by a\nPV generator, a boost converter, a Pulse Width Modulation and a DC motor....
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